J/ApJ/710/613 Broad HI absorbers (Danforth+, 2010)
Broad H I absorbers as metallicity-independent tracers of the warm-hot intergalactic medium. Danforth C.W., Stocke J.T., Shull J.M. <Astrophys. J., 710, 613-633 (2010)> =2010ApJ...710..613D (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; H I data ; Spectroscopy ; Ultraviolet ; QSOs Keywords: cosmological parameters - cosmology: observations - intergalactic medium - quasars: absorption lines - ultraviolet: general Abstract: We compile a catalog of reliable BLA (thermally broadened Lyα absorber) candidates along seven active galactic nucleus sight lines from a larger set of Lyα absorbers observed by the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST). We compare our measurements based on independent reduction and analysis of the data to those published by other research groups. We examine the detailed structure of each absorber and determine a reliable line width and column density. Purported BLAs are grouped into probable (15), possible (48), and non-BLA (56) categories. Based on 164 measured curve of growth (COG) HI line measurements, we statistically correct the observed line widths via a Monte Carlo simulation. Finally, we present new, high signal-to-noise ratio observations of several of the BLA candidate lines from Early Release Observations made by the Cosmic Origins Spectrograph on HST. Description: Until the recent installation of the Cosmic Origins Spectrograph (COS), the best data for a BLA search come from recent STIS echelle spectroscopy, which typically features the highest S/N combined with a spectral resolution sufficient to resolve HI lines of widths less than ∼30km/s. Lehner et al. (2007ApJ...658..680L) produced a large compilation of seven AGN sight lines and ∼100 candidate BLAs based on b-values≥40km/s. Late in the analysis process, we obtained observations of PKS 0405-123 by the HST/COS (J. Green et al. 2012ApJ...744...60G; S. Osterman et al. 2010arXiv1012.5811O) as part of its public Early Release Observations (ERO) program. These data were obtained in the G130M grating (1132Å<λ<1468Å) with a nominal resolution R∼20000 (Δv=15km/s). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 131 7 Broad Lymanα (BLA) sample sight lines table2.dat 166 119 Probable, possible, and non-BLA absorbers
See also: J/ApJS/182/378 : HI and OVI absorbers in nearby Universe (Wakker+, 2009) J/ApJ/701/1219 : Galaxy survey in 3 QSO fields (Chen+, 2009) J/ApJ/679/194 : Low-z intergalactic medium. III. (Danforth+, 2008) J/ApJ/636/631 : Lyman-alpha forest toward PKS 0405-123 (Williger+, 2006) J/ApJS/164/1 : IGM absorbers toward HE 0226-4110 (Lehner+, 2006) J/ApJ/643/680 : Imaging and spectroscopy around PKS 0405-123 (Prochaska+, 2006) J/ApJS/155/351 : Absorption toward PG 1116+215 (Sembach+, 2004) J/ApJ/617/718 : Atomic data and EW for PKS 0405-123 (Prochaska+, 2004) J/ApJ/524/536 : Nearby Lyα quasar absorbers (Impey+, 1999) J/ApJ/508/200 : QSO low-z Lyα absorbers (Tripp+, 1998) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 12 A12 --- AGN Sight line 14- 15 I2 h RAh Hour of right ascension (J2000) 17- 18 I2 min RAm Minute of right ascension (J2000) 20- 23 F4.1 s RAs Second of right ascension (J2000) 25 A1 --- DE- Sign of declination (J2000) 26- 27 I2 deg DEd Degree of declination (J2000) 29- 30 I2 arcmin DEm Arcminute of declination (J2000) 32- 33 I2 arcsec DEs Arcsecond of declination (J2000) 35- 39 F5.3 --- zAGN AGN redshift 41- 45 F5.3 --- Delz Maximum absorption path length (Δzmax) 47- 51 F5.3 --- DelX Cosmologically corrected maximum path length (ΔXmax) 53-131 A79 --- Ref Reference (1)
Note (1): Most recent detailed STIS/E140M analysis; all are also included in Lehner et al. (2007ApJ...658..680L) and Danforth & Shull (2008, Cat. J/ApJ/679/194).
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 A2 --- Abs Probable, Possible or Non-absorber category (1) 4- 15 A12 --- AGN Sight line 17- 23 F7.5 --- zabs Absorption redshift 25- 27 I3 km/s b1 ? Line width of component 1 (2) 28 A1 --- u_b1 [:] Uncertainty flag on b1 30- 31 I2 km/s E_b1 ? Positive error on b1 33- 34 I2 km/s e_b1 ? Negative error on b1 36- 37 I2 km/s b1d ? Second b1 value 39- 41 A3 --- n_b1 [COG/Nd/Nm ] Note on b1 (3) 43- 47 F5.2 [cm-2] logN1 ? Log of HI column density of component 1 48 A1 --- u_logN1 [?:] Uncertainty flag on logN1 50- 53 F4.2 [cm-2] E_logN1 ? Positive error on logN1 55- 58 F4.2 [cm-2] e_logN1 ? Negative error on logN1 59- 60 A2 --- n_logN1 [Nd/Nm] Not detected or Not measured (3) 62- 64 A3 --- Ref Reference (4) 66- 68 I3 km/s b2 ? Line width of component 2 (2) 69 A1 --- u_b2 [:] Uncertainty flag on b2 71- 72 I2 km/s E_b2 ? Positive error on b2 74- 75 I2 km/s e_b2 ? Negative error on b2 77- 78 I2 km/s b2d ? Second b2 value 80- 82 A3 --- n_b2 [COG/Nd/Nm/bl ] Note on b2 (3) 84 A1 --- l_logN2 Limit flag on logN2 85- 89 F5.2 [cm-2] logN2 ? Log of HI column density of component 2 91- 94 F4.2 [cm-2] E_logN2 ? Positive error on logN2 96- 99 F4.2 [cm-2] e_logN2 ? Negative error on logN2 101-102 A2 --- n_logN2 [Nd/Nm] Not detected or Not measured (3) 104-107 A4 --- Ref2 Reference (4) 109-111 I3 km/s b0 ? Mean line width (2) 112 A1 --- u_b0 [:] Uncertainty flag on b0 114-115 I2 km/s b0d ? Second b0 value 117-119 A3 --- n_b0 [COG/LW* ] Note on b0 (3) 121-125 F5.2 [cm-2] logN0 ? Log of mean Hydrogen column density 126-127 A2 --- n_logN0 [Nd] Nd: Non detected (3) 129-166 A38 --- Notes Absorber notes
Note (1): Category as follows: Pr = Probable BLA. There is no definitive test for BLAs, but we classify as "probable" any system with well-defined bCOG≥40km/s or bLW>60km/s ("LW" for Lyα line width; "COG" for curve of growth) confirmed by independent measurement of Lehner et al. (2007ApJ...658..680L) and ourselves and with no obvious sign of multiple component structure (such as an asymmetric profile) in Lyα or higher Lyman lines or metal ions (if available). Fifteen systems fall within this category. Note that we do not a priori use the presence or absence of OVI, NV, or other warm-hot intergalactic medium (WHIM) sign posts as a BLA determinant, although several OVI detections are present in this sample. Po = Possible BLA. Less likely than category A, the "possible" category includes systems with 40km/s≤bLW≤60km/s. This category also holds intermediate cases, where an absorber shows ambiguous component structure or a high degree of uncertainty as to line width and/or continuum fit, but a broad HI system component cannot be reasonably ruled out. Forty-eight HI absorbers fall in this category. No = Non-BLA. Nearly half (56/119) of the HI lines with b≥40km/s published by Lehner et al. (2007ApJ...658..680L) or Danforth & Shull (2008, Cat. J/ApJ/679/194) are most likely not BLAs by our assessment for a variety of reasons: measured bCOG<40km/s or bLW<40km/s; probable alternate line identification; obvious narrow component structure; or simply not detected as absorption features in our reduction of the data. Note (2): Line width is usually denoted in terms of the corresponding Doppler parameter b∼FWHM/2(ln2)0.5~(2σ)0.5 where σ is the Gaussian width. See section 1 for further details. Note (3): Flag as follows: Nd = Non detected Nm = Non measured LW = Lyα line width COG = curve of growth Note (4): Measurement sources as follows: L07 = Lehner et al. 2007ApJ...658..680L (and sources therein); DS08 = Danforth & Shull 2008, Cat. J/ApJ/679/194; W06 = Williger et al. 2006, Cat. J/ApJ/636/631; S05 = Savage et al. 2005ApJ...626..776S; S04 = Sembach et al. 2004, Cat. J/ApJS/155/351; R04 = Richter et al. 2004ApJS..153..165R; This = this work.
History: * 13-Mar-2012: From electronic version of the journal * 29-Apr-2012: "PG 0953+414" converted into "PG 0953+415" in table1, to be in coherence with the table2. Both names are found in the literature but refer to the same AGN.
(End) Emmanuelle Perret [CDS] 13-Mar-2012
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